I think spencer's views are supported in ponnyin selvan.
Spencer talks about declining revenues of cholas. kalki talks about the same.paluvettarayar's major complaint is that the treasury is empty.
Spencer talks about inter rivalry between sitrarasars. Kalki says the same thing.Some local kings like paluvettarayar were even controlling chola kingdom according to kalki.
My guess is during sundara chola regime,local kings' influence grew considerably.Maybe in uthama cholas regime the situation worsened.Maybe Rajaraja and Rajendra reversed this trend later on.